Have a look online from google and I saw they lay eggs in or on floating plants. There was a video showing this. Also I read they need soft water. How large were the pair you tried. When the Zebra Danios are out of my breeding tank i will try and then tell you if I had success with the Harlequins Thanks for your replyI have tried to breed them before and didn't have any luck, they are quite difficult with their water parameters.